package com.hs.monitor.encrypt;

import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * 如果通信过程中需要非对称加密,可以引用此类实现
 */
public class RSAEncrypt {

    private static final String message = "hs-will-be-better";
    private static String publicKeyString;
    private static String privateKeyString;

    public static void main(String[] args) throws Exception {
        //生成公钥和私钥
//        genKeyPair();
        //加密字符串

//        System.out.println("随机生成的公钥为:" + publicKeyString);
//        System.out.println("随机生成的私钥为:" + privateKeyString);
//        String messageEn = encrypt(message, publicKeyString);
//        System.out.println(message + "\t加密后的字符串为:" + messageEn);
//        String messageDe = decrypt(messageEn, privateKeyString);
//        System.out.println("还原后的字符串为:" + messageDe);
    }

    /**
     * 随机生成密钥对
     *
     * @throws NoSuchAlgorithmException
     */
    public static void genKeyPair() throws NoSuchAlgorithmException {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        // 初始化密钥对生成器，密钥大小为96-1024位
        keyPairGen.initialize(2048, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        // 得到私钥字符串
        privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
    }

    /**
     * RSA公钥加密
     *
     * @param msg       加密字符串
     * @param publicKey 公钥
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static byte[] encrypt(byte[] publicKey, byte[] msg) {
        try {
            //base64编码的公钥
            byte[] decoded = Base64.decodeBase64(publicKey);
            RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
            //RSA加密
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
//        String outStr = Base64.encodeBase64String(cipher.doFinal(msg));
            byte[] bytes = cipher.doFinal(msg);
            return bytes;
        } catch (Exception e) {
            System.out.println("加密异常---返回原明文数据");
            e.printStackTrace();
            return msg;
        }
    }

    /**
     * RSA私钥解密
     *
     * @param msg        加密字符串
     * @param privateKey 私钥
     * @return 铭文
     * @throws Exception 解密过程中的异常信息
     */
    public static String decrypt(String msg, String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(msg.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }
}

